Removing iron from water



.April 3, 1941- J. P. LAwLoR nu, 2.237.882

REIIOVING IRON FROI WATER umm n tamed Apr.. s, '1941 2,221,882 REMOVINGIRON FROM WATER Joseph P. Lawlor and Vincent M. Roach, Ames, Iowa,assignors to General Filter Company,

Ames, Iowa, a corporation of Iowa Application December 6, 1937, SerialNo. 178,396

(Cl. ZIO-26) 11 Claims.

This invention relates to removing iron from water, together with othercompounds, gases, and odors.

An object ofl the invention is to provide a simple and effective methodand means for removing iron from well waterl and other water, togetherwith other undesirable solids and gases. A further Objectis to provide asimple method and means for rendering iron compounds insoluble throughthe use of air and removing the compounds through ltration, while at thesame time preventing and substantially reducing the absorption into thewater ofcertain constituents of the air. Other specific obiects andadvantages will appear as the speciflcation proceeds.

The invention is illustrated, in a preferred embodiment, by theaccompanying drawing, in which- Figure 1 is a side elevational view ofapparatus embodying our invention, the tank being shown in section; Fig.2, a broken enlarged vsectional view of the air diffusing means; andFig. 3, a vertical sectional view of the air release mechanism.

Cil

In the illustration given. A designates the main l tank; B, means fordiffusing the air throughout the water stream; and C, automatic meansfor releasing the air. 'Ihe tank A may be of any suitable construction.We prefer to employ a tank having a dome-shaped top I to which issecured centrally a riser the riser II having a horizontal sectionturned to communicate-with the air release member C. In the lowerportion of the tank are placed certain filtering materials, including atop layer I2 of sand and lower'layers I3 of more ,A coarsely formedfiltering materials. Appipe Ilextends into the lower portion of the'tankand is provided with outwardly extending pipes I 5 hav- `ing orifices I6in their lower sides. By this means,

water can be withdrawn from the lower portion of. the tank and, when itis desired to reverse the flow in order to cleanse the filteringmaterial, this means is employed for introducing water into the tank.

The fresh water inlet pipe I1 enters tank A near its top and is upwardlyturned at its end and provided with a circular baille plate I8. Betweenthe baille plate I8 and the sand layer I2 is a free board or surge spacein which the sand may be moved and' allowed to settle during the backwashing operation.v

The air diffusing apparatus B is located within the fresh Water inletpipel I1 outside tank A and ymay also be of any suitable construction.In the illustration given, the member B comprises an enlarged cylinderI9 closed at its ends by flanges 20, the flanges being connected to thepipe I1.

. Within the chamber provided by cylinder I9 and flanges 20 is supportedan air diffusing device consisting of a cylinder 2| having minuteopenings therethrough. Any cylinder affording extremelyminute openingsis suitable for the pur-` pose. -We have yfound a cylinder formed ofmaterial known as carborundum stone satisfactory. The ends of thecylinder 2| are closed by plates 22, and the plates 22 are confinedagainst the ends of the cylinder so as to close the same by theengagement of nuts 23 and 24 with the threaded portions of the air inletpipe 25, as shown more clearly in Fig. 2. The lower end of the pipe 25is closed by a plug 26. Pipe 25 communicates with an air compressor (notshown). It is important that that portion. of the inlet pipe I1 whichextends above the diffuser B extend either in an upward direction or ina horizontal direction so as to avoid air locks and so as to feed thewater and the air uniformly mixed therewith in a constant and even flowinto the upper portion of tank A. A valved pipe 21 communicates withpipe I1, as shown more clearly in Fig. 1, and leads to a sump or sewer.v

Ihe air separatingapparatus C is of well known i construction and neednot be described in detail.

'It consists of a casing 28 provided at its upper side with an outlettting 23 providing a valve seat 30. A valve stem 3| is carried bythe oatl lever 32 pivotally secured at its free end to the casing 28 at 33 andhaving `its other end provided with a water float 34. Air risercommunicates with the top of casing 28 and a riser 35 joins the`Operation In operation, 'fresh water `from the pump is forced' throughinlet pipe I 1 into the Yenlarged chamber provided by cylinder 9.Simultaneously compressed air is passed through pipe 25 into thediffuser 2|, the air escaping through the'ttings 40 into the upperportion of the chamber and thence escaping through the minute openingsin the cylinder 2| to the 'enlarged chamber outside. By introducing thevair into the upper portion of cylinder 2|, the air does not tend tochurn any chamber C will be substantially the same.

liquid which might be within the cylinder to any great extent but passesrapidly through the walls of cylinder 2l into the stream of wateroutside.

As the air passes out of the minute openings in finely divided form, itforms extremely minute bubbles which are constantly washed ofi thesurface of cylinder 2| and carried by the rapidly moving stream of waterupwardly, thus preventing the bubbles from coalescing and causing themto be uniformly distributed throughout the cross section of the liquidstream. This action results in bringing the oxygeny of the air into theintimate contact with the soluble iron compounds in the stream andbrings about an oxidation of such compounds, thus renderingtheminsoluble and thus removable by filtration. Simultaneously, theoxidation and aeration produce other desirable changes in compoundscarried by the water so that they may be removed by filtration, theevolved gases being removable later with the air. The water stream thuscharged uniformly with the great body of minute bubbles passes into theupper portion of tank A, the course being that of upward inclination or.along a horizontal path. The stream discharges into tank A above bafflei 8, as indicated by arrows in Fig 1.

Tank A is preferably kept charged with water,

the level being maintained about midway of the air outlet mechanism 28and the vertical portion of riser il. It will`be understood, however,that the level of the liquid may be dropped to a. lower mint while stillcarrying out the spirit of our invention. linlet pipe Il, diffuser B,and tank A are preferably kept under super-atmospheric pressure in orderto bring about prompt vand eective oxidation of the iron compounds.Usuallythe pressure varies from 45 to 70 pounds, and the pressuressometimes exceed both of these limits. The usual pressure ranges between50 to 60 pounds per square inch.4

The water passing through the diffusing device B iiows from the inletpipe I1 into the tank A and into the riser 354 leading to the releasing`means C. Since the tank A communicates with the releasing chamber Cthrough the riser Il, the level of the water in the riser Il and the Asthe operation is` carried on, air passes through the riser i I to thechamber C.

As the process continues, the air in the riser il and the chamber Cincreases in pressure and forces the water level andthe oat 34downwardly. This lowers the valve stem 3l from the as far as ourknowledge goes, have been unsuccessful.

We have discovered that by maintaining a small body of water above themain body and withdrawing the air from the small body, that thisundesirable result can be avoided. The cross section of the small bodyof water being extremely limited, there is thus maintained above 'it arelatively small air surface so that the degreeof absorption of nitrogenor other gases is proportionately reduced. With the new processdescribed herein, the presence of white water Where ordinary pressures,such as from 50 to 60 pounds, are employed, cannot be detected, assumingthat the amount of free air introduced is properly controlled.

In the process described, the only surfaces wherein the water contactsthe air body are those in riser il and in the member C. These surfacesare greatly less than those which would be encountered if the topportion-of tank A were filled with air so that there is a.correspondingly lower fractional absorption of the gases. In this sameconnection, it will be noted that evolved gases which may containdisagreeable` odors, etc., are likewise maintained to a much greaterdegree out of contact with the main body of water and the absorptionthereof is much decreased.

We have also discovered that another cause for white water is theintroduction of too much may be introduced into the pipe I1. In the casevalve seat 30, permitting air to escape through the outlet 29. When theair is released, the pressure within the chamber C and the riser il isdecreased and the water level rises, lifting the float 34 -and closing,the release valve. l'i'he process of releasing the air is thus automaticand self-controlling. f

' if the water level is allowed to remain well within tank A, so that asubstantial body of air is enclosed' in the space above the water leveland the top of the tank at such pressures as are usually employed in thesystem, there is a substantial absorption by the water of certainconstituents of the air, such as, for example, nitrogen, and suchconstituents remain inthe water until it is later released from thefaucet by the consumer. when the water is released, the nitrogen orother gases immediately forms a large number of smallbubbles producingwhat is commonly known as white water. This result is undesirable andvarious suggestions and plansl have been evolved to avoid it, all ofwhich,

of very high pressure, such as pounds, two cubic feet per gallons ofwater is found to be excessive and it results in white water. frWith theusual pressures of from 50 to 60 pounds, we find that the preferredquantity of air is approximately one cubic foot ,of free air to i00gallons of water. Above 60 pounds pressure, an amount of air less thanone-cubic foot per 10'0 gallons of water should be introduced, theamount being reduced in. accordance with the pressure. However, when thelamount of free air drops much below one-half cubic foot, the oxidationis usually found to be unsatisfactory.

yOn the other hand, when pressures are dropped below 40 pounds, we findthat free air can be introduced in excess of two cubic feet per 100gallons of water. From the foregoing, one skilled in the art can readilydetermine the proper amounts of free air which are to be introduced intothe system per 100 gallons of Water in order to avoidwhite water whileat vthe same time producing effective oxidation.

' As stated above, another important factor in addition to pressure isthe length of time that the air 'remains in contact with the water, andthis factor' influences the foregoing conclusions. We prefer to withdrawthe air as quickly as possible from the water. The farther the diffuseris located from the tank and the longer the conduit connecting thediffuser and the tank A, the greater the length of time that the airremains in contact with the Water. We prefer to have the diffuserlocated adjacent the tank A with upwardly inclined or horizontal pipesso th'at the air will pass rapidly from the diffuser into tank A andthence escape. With this arrangement, we find that the air escapes inless than a minute. Under normal conditions, we find that it escapes inlthe neighborhood of ten seconds.

The water from tank A is withdrawn after the same has passed through thefiltering layers through pipe i4 into the main lines for the city orinto the storage tank. 'Ihe iron cbmpounds and other compounds which arerendered insoluble are thus removed in the filter layers. It will benoted that the entire filtration is carrled on within tank A itself andis not accoinplished in separate and additional apparatus known assettling chambers, etc. as have heretofore been found necessary.

In cleansing the filtering layers, fresh water is forced through pipe Iland upwardly through the filtering layersvi! and i3 and thence outthrough pipe I1 and thence through pipe 2T vto the sewer. a valve (notshown) in pipe i1 being closed so as to prevent the water from passingthrough diffuser B. In @his operation, the baiiie .IB causes the waterto pass uniformly through the filtering layers so as toremove theforeign materials from all parts thereof.

The apparatus shown is extremely simplebut effective in carrying out theprocess described. It is sometimes found that the valve 3i inthe airseparator C becomes lclogged with ironr or other compounds. We find thatsuch foreign matter can be readily removed by opening valve 38, valve 39in pipe 35 being closed. This causes liquid to pass from tank A andthrough riser ii downwardly upon float valve 3l, thus depressferred, itwill be understood that these are illustrative only and that the' samemay be modified greatly without departing from the spirit of ourinvention.

The foregoing detailed description has been given for clearness ofunderstanding only, Aand no unnecessary limitationsl should beunderstood therefrom', but the appended claims should be construed asbroadly as permissible, in view of the prior art.

We claim:

1. In a process for the purposes set forth, the steps of maintaining abody'ofl water in a restricted zone and under pressure of from 50 to 60pounds, maintaining the level of water insaid zone sufficiently high toprevent the exposure to air of any substantial portion of said body ofwater, passing fresh water in a confined stream into said body,introducing compressed airuinto saidwater in the proportion ofapproximately one cubic foot of free air to 100 gallons of water,

stricted zone under pressures in excess of 60 pounds, sa' zone beingsubstantially V filled by said body '-o water whereby only a very smallportion of the surface of said body of' water may be exposed to air,passing a stream of fresh water into said body, introducing air underpressure into said stream in the proportion of not less than one-halfcubic foot and not greater than one cubic foot offree air for each 100gallons of water, the air being introduced in finely divided form so asto form minute bubbles in said'stream. lwithdrawing the air quickly fromthe body, and filtering and withdrawing water from said body.

3. In a process for purifying water by removing iron therefrom, thesteps of maintaining a body of waterunder pressure within a restrictedzone wherein only a small portion of the surface of said body'is exposedto air, maintaining a second much smaller body of water within arestricted zone and communicating with said first* mentioned bodyadjacent the top thereof, passing fresh water in a conflnedstreamI intosaid first-mentioned body, said stream being introduced into said bodybelow the surface` thereof. introducing air into said stream underpressure and in finely divided form to produce minute air bubblesthroughout a cross section of said stream, withdrawing said air fromsaid first-mentioned body to the zone of said smaller body, withdrawingair from the zone of said second-mentioned body of water, and filteringand withdrawing water from said first-mentioned body.

4. In a'process for purifying water by removing iron therefrom, thesteps of maintaining a main body of water under pressure within arestricted zone'wherein'only a small portion of the -surface of saidbody is exposed to air, passing small body of water, and vltering andwithdrawing water from said mainfbody.

5. In a process for purifying water by removing iron therefrom whilepreventing the absorption of large amounts of air by said water, thesteps of maintaininga' main body of water under pressures in excess of40 pounds in a restricted zone wherein only a small portion of thesurface of said body of water is exposed to air, rapidly passing freshwater in a confined stream and under pressures in excess of 10 poundsinto said main body of water, introducing into said stream air underpressure and in an4 amount not in excess of 2 cubic feet of air for each100 gallons of water, the Aair being in finely divided form and formingminute bubbles in said stream and being introduced into said stream at apoint closely adjacent said main'l body, maintaining a much smaller bodyof water in communication with the top portion of said main body, thesurface of said smaller body being exposed to air,l withdrawing said airfrom said main body of water to a position above saidv smaller body ofwater, `and withdrawingrair from said position above the smaller body ofwater.

6. In a process for purifying water by removing iron therefrom, thesteps of maintainingJ a tank filled with water under superatmosphericpressure, passing fresh water in a. confined stream and under.superatmospheric pressure into said tank, introducing air into saidstream before it enters said tank, said air being introing into saidoutlet conduit, maintaining the water in said outlet at a level abovethe top of said tank, withdrawing said introduced air through said airoutlet, and filtering the water in said tank.

7. In a process` for purifying water by removl0 ing iron therefrom, thesteps of flowing water to be treated under superatmospheric pressure andin a confined stream while discharging air in finely divided form intosaid stream to produce minute bubbles therein, maintaining a main bodyof water in a restricted zone and under super- A atmospheric pressure,said zone being substantially'iilled by said body of water whereby onlya small portion of the surface of said body of atmospheric pressure intosaid main body of water, introducing air in finely divided form intosaid stream of water, providing a smaller body of water communicatingwith said main body but being much smaller than said main body,

' quickly withdrawing said introduced air from the main body of water toa position above the smaller body, and withdrawing said introduced atank, iiltering materials supported in the lower portion oi'v said tank,means for withdrawing filtered water from the lower portion of the tank,v

a fresh water inlet pipe communicating with said tank for passing 4astream of water thereinto, means in said inlet pipe adjacent said tankfor introducing air in nely divided form into the stream of water insaid inlet pipe, producing water may be exposed to air, passing saidstream minute bubbles in said stream, an air outlet conof watercontinuously into said body of water, removing said introduced airquickly from said body of water and out of contact with said body oi'water wherebyvthe air is removed from said body of water without beingsubstantially absorbed thereby, and filtering said body of water. 8. lna process for the purposes set forth, the

steps of maintaining a body of water in a restricted zone underpressures in excess of 40- pounds, said zone being substantially filledby under pressure not in excess of two cubic feet of I free air for eachgallons of water, the air being in ilnely divided form and formingminute Vbubbles. in said stream, removing the air quickly from saidbody,and filtering and withdrawing -water from said body.

9. In a process for purifying water by removing iron therefrom, thesteps of maintaining a main body of water within a restricted zone andunda'.` superatmospheric pressure, said zone be- 'ing substantiallynlled by said water whereby 45 water,

only a small portion of the surface of the main body of water is exposedto air, passing fresh water in a confined stream and under superduit ofrelatively small cross sectional area communicating with said tank andextending above the top of the same, means for maintaining water in saidtank Withthe water extending into said outlet conduit, the level of theWater in said outlet conduit being maintained above the top of saidtank, and means for withdrawing said introduced air through said airoutlet.

il. In a process for purifying water by removing iron therefrom, thesteps of owing water to be treated under superatmospheric pressure andin a confined stream while discharging air in nely divided forminto saidstream to produce minute bubbles therein, maintaining a main body ofwater in a restricted zone and under superatmospheric pressure, saidzone being substantially filled by said body of water whereby only asmall portion of the surface of said body of water may be exposed toair, passing said stream of water continuously into said body of water,removing said introduced air quickly from said body of water whereby theair is removed from said body of .water without being substantiallyabsorbed thereby, and filtering said body of JOSEPH P. LAWLOR. VINCENTM. ROACH.

